The present invention generally relates to message control systems for data communication systems, and more particularly to a system for controlling messages among a plurality of processing modules which form a loosely coupled multiprocessing (LCMP) system.
In data communication systems, one of the most important factors is to realize a reliable system having a large processing capability. In order to satisfy this demand, multiprocessor systems have been used recently. As one of the system configurations of the multiprocessor system, there is the loosely coupled multiprocessing (LCMP) system in which a plurality of independent computers are coupled by channel-to-channel adapters and the like to enable a job input and execution by any of the computers.
When implementing a message communication in the loosely coupled multiprocessing system, it is necessary to realize a message communication which is initiated on the transmitting side, and appropriately cope with the various control end requests issued during the communication by the data processing function. In addition, it is necessary to realize a message control system which can simply set and release logical connections.
2. Description of the Related Art
As a data communication system having a microprocessor structure, a tightly coupled multiprocessing (TCMP) system having a system configuration in which a plurality of microprocessors share a single memory device was widely used conventionally. However, the loosely coupled multiprocessing system system in which each processor has its own memory device is more popular to improve the system performance when increasing the number of processor modules.
According to the message control system of the loosely coupled multiprocessing system, the data processing part which is the software within the processing module at the origin of the transmission request conventionally executes the message communication via the hardware which manages the communication process or, the transmission and reception process is started after the software of the transmitting side processing module and the software of the receiving side confirm the issuance of the message transmission and reception process.
In addition, the process of setting the logical connection relationship between the transmitting side processing module and the receiving side processing module is executed according to the communication process which is executed prior to the message communication of the message which is the subject of the communication. On the other hand, the release process of the above logical connection relationship is executed according to the communication process which is executed after the message communication ends.
In the conventional message control system, if the message communication is executed via the software, the software cannot execute the original data processing during the message communication. In addition, in the case of the conventional system which confirms the issuance of the message transmission and reception process at the transmitting side and the receiving side, the progress of the data processing is delayed.
Furthermore, according to the conventional message control system, it is necessary to execute the communication process for setting and releasing the logical connection relationship respectively before and after the message communication. As a result, the control process for setting and releasing the logical connection relationship becomes complex.
Moreover, the conventional system cannot transmit the message when the transmitting side processing module wishes to transmit. Even if the hardware managing the signal processing were to carry out the message communication totally without the need for software intervention so as to make the transmitting side initiated message communication and the transmitting side processing module transmit the message when it wishes, it becomes impossible to cope with the forced end request of the message communication required by the software.